• Journal of Digital Convergence
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• v.11 no.12
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• pp.447-452
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• 2013

Berkley Media Access Control (B-MAC) protocol is one of the well-known MAC protocols, which uses adaptive preamble sampling scheme and is designed for wireless sensor networks (WSN). In this paper, we are reviewed about security vulnerability in B-MAC, and analyzed the power which is consumed at each stage of B-MAC protocol according to vulnerability of denial of sleep(DoS) and replay problem. From our analytical results, it can be considered the need of power efficient authentication scheme which provides the reliability, efficiency, and security for a general B-MAC communication. This is the case study of possible DoS vulnerability and its power consumption in B-MAC.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.3
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• pp.156-162
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• 2020

Wireless Sensor Network (WSN) field is mainly studied to monitor and characterize large-scale physical environments to track various environmental or physical conditions, such as temperature, pressure, wind speed and humidity. WSN can be used in various applications such as wild surveillance, military target tracking and monitoring, dangerous environmental exploration and natural disaster relief. We design probabilistic mobile models that apply to mobile ad hoc network mobile environments. A probabilistic shift model proposed by dividing the number of moving nodes and the distance of travel into two categories to express node movement characteristics. The proposed model of movement through simulation was compared with the existing random movement model, ensuring that the width and variation rate of the first node node node node (FND) was stable regardless of the node movement rate. In addition, when the proposed mobile model is applied to the routing protocol, the superiority of network life can be verified from measured FND values. We overcame the limitations of the existing random movement model, showing excellent characteristics in terms of energy efficiency and stable in terms of changes in node movement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.4760-4765
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• 2010

Time out-medium access control (T-MAC) protocol is one of the well-known MAC protocols designed for wireless sensor networks (WSN), and is proposed to enhance the poor performance of the S-MAC protocol. In this paper, we are reviewed about security vulnerability in T-MAC, and analyzed the power which is consumed at each stage of T-MAC protocol according to vulnerability of denial of service (DoS) and replay problem. From our analytical results, it can be considered the need of power efficient authentication scheme which provides the reliability, efficiency, and security for a general T-MAC communication. This is the case study of possible DoS vulnerability and its power consumption in T-MAC.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5B
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• pp.557-565
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• 2011

In this paper, we assume that sensor nodes organize the multi-hop networks, are fixed, and operate as full function devices(FFD). The wireless sensor network(WSN) only consists of mobile nodes without the assistance from the fixed infrastructure, which increases the flexibility of the network. However, it is difficult to perform routing in the WSN, since sensor nodes freely join in and drop out of the network, and some sensor nodes have very low power. We propose the algorithm combining routing schemes based on the bitmap and cluster methods in this paper. Through computer simulations, we show the validity of the proposed algorithm.

• Journal of Korea Multimedia Society
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• v.19 no.12
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• pp.2014-2023
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• 2016

Web presence is one of the key issues for extensive deployment of Internet-of-Things (IoT). An obstacle to overcome for Web presence is relatively low computing power of IoT devices. In this paper, we present implementation of an IoT platform based on Constrained Application Protocol (CoAP) which is a web transfer protocol proposed by Internet Engineering Task Force (IETF) for the low performance IoT devices such as Wireless Sensor Network (WSN) nodes and micro-controllers. To qualify the performance of CoAP-based IoT system for such an application as smart grid, we designed a test platform consisting of Raspberry Pi2, Kmote WSN node and a desktop PC. Using open source softwares, CoAP was implemented on top of the platform. Leveraging the GET command defined at CoAP specification, performance of the system was measured in terms of round-trip time (RTT) from web application to the Kmote sensor node. To investigate abnormal cases among the test results, hop-by-hop delays were measured to analyze resulting data. The average response time of CoAP-based communication except the abnormal data was reduced by 23% smaller than the previous research result.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.4
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• pp.759-766
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• 2015

This paper proposes a location-based key management scheme in wireless sensor networks, and among the existing location-based key management techniques, we focused on the LDK (Location Dependent Key management). In order to improve the problems occurred by communication interference, we introduced the key revision process and the method of key establishment using grid information. According to the simulation of this scheme, it increased connectivity while decreased compromise ratio than those of the previous LDK, futhermore, we confirmed that a hexagon distribution of AN reduces the network cost.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.796-805
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• 2016

In many wireless sensor network (WSN) applications, the information transmitted by an individual entity or node is of limited use without the knowledge of its location. Research in node localization is mostly geared towards multi-hop range-free localization algorithms to achieve accuracy by minimizing localization errors between the node's actual and estimated position. The existing localization algorithms are focused on improving localization accuracy without considering efficiency in terms of energy costs and algorithm convergence time. In this work, we show that our proposed localization scheme, called DV-maxHop, can achieve good accuracy and efficiency. We formulate the multi-objective optimization functions to minimize localization errors as well as the number of transmission during localization phase. We evaluate the performance of our scheme using extensive simulation on several anisotropic and isotropic topologies. Our scheme can achieve dual objective of accuracy and efficiency for various scenarios. Furthermore, the recently proposed algorithms require random uniform distribution of anchors. We also utilized our proposed scheme to compare and study some practical anchor distribution schemes.

• Industrial Engineering and Management Systems
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• v.16 no.1
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• pp.92-102
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• 2017

In this paper, we consider a typical health care system via the help of Wireless Sensor Network (WSN) for wireless patient tracking. The wireless patient tracking module of this system performs localization out of samples of Received Signal Strength (RSS) variations and tracking through a Particle Filter (PF) for WSN assisted by multiple transmit-power information. We propose a modified PF, Kullback-Leibler Distance (KLD)-resampling PF, to ameliorate the effect of RSS variations by generating a sample set near the high-likelihood region for improving the wireless patient tracking. The key idea of this method is to approximate a discrete distribution with an upper bound error on the KLD for reducing both location error and the number of particles used. To determine this bound error, an optimal algorithm is proposed based on the maximum gap error between the proposal and Sampling Important Resampling (SIR) algorithms. By setting up these values, a number of simulations using the health care system's data sets which contains the real RSSI measurements to evaluate the location error in term of various power levels and density nodes for all methods. Finally, we point out the effect of different power levels vs. different density nodes for the wireless patient tracking.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.6 no.4
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• pp.208-215
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• 2013

In recent years, many applications in WSN have increasingly interested in data transfer reliability. In this paper, we propose a dynamic grouping transfer mechanism which maintains both reliability and energy efficiency in transmission from a source to a sink. The proposed scheme considers channel error of each node. Then it uses an end-to-end ACK transmission in a group and a hop-by-hop ACK transmission between groups. Consequently this mechanism minimize the cost of packet transfer along with enhancing the network lifetime and reliability.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.57.1-57.1
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• 2011

본 논문에서는 소음을 저감하고 구조적 안전도를 향상시키기 위하여 10kW급 소형 복합재 풍력터빈 블레이드를 해석, 설계하였다. 풍력터빈 블레이드 설계의 기본 사항에 맞추어 블레이드의 스팬 길이는 약 4m, 중량은 30kg 내외가 되도록 설정하였다. 풍력발전기용 블레이드는 경량화가 중요하므로 유리섬유복합재 (glass fiber reinforce pastics), 탄소섬유복합재 (carbon fiber reinforced plastics)가 사용되었다. 본 설계에서는 Carbon prepreg (WSN3KY), Carbon UD(UIN150c), E-glass 등을 사용하였다. 상용 유한요소 프로그램인 NASTRAN을 이용해 Carbon prepreg (WSN3KY), Carbon UD (UIN150c)의 탄소섬유복합재만으로 구성된 블레이드 구조해석을 수행한 결과 중량 조건 및 강도의 안전도는 충족되었으나, 높은 가격을 감안하여 E-glass와 조합하여 블레이드를 재설계할 예정이다. 이번 설계는 소형 풍력발전용 블레이드 설계이므로 좌굴은 고려하지 않았으며, 향후 필요에 따라서 좌굴 및 피로해석도 수행하여 검증할 예정이다. 그리고 블레이드가 복합재로 구성되면 감쇠력이 감소할 가능성이 있다. 탄소섬유복합재로만 구성된 블레이드 구조해석에서도 최대 40cm의 변형이 예측되었으며, 감쇠값 저하 문제도 고려하여야 될 것 같아 BEMT (Blade Element Momentum Theory) 공력모델을 이용해 구조-유체 연성 결합 해석을 수행할 계획이다.